The very best point of sale product on the mac
http://www.xsilva.com

LightSpeed™ is a ground-breaking, next-generation Point of Sale system for Mac that offers retail stores comprehensive and easy-to-use retail tools in an iTunes-like Browser, and an innovative floating POS interface designed for high-speed, error-free checkout. A tightly-integrated Web Store module (sold separately) allows stores to take their product catalog online and download orders right back into LightSpeed. All of this functionality is built on a powerful, multi-user database that will scale to satisfy the needs of any growing retail business.